Borrowings Securities Sold under Agreement to Repurchase (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Securities Sold under Agreements to Repurchase	$ 155,388	$ 185,763
U.S. Treasury securities and obligations of U.S. government corporations & agencies
Short-term Debt [Line Items]
Securities Sold under Agreements to Repurchase	100,895	100,526
US States and Political Subdivisions Debt Securities [Member]
Short-term Debt [Line Items]
Securities Sold under Agreements to Repurchase	0	1,173
Mortgage-backed securities
Short-term Debt [Line Items]
Securities Sold under Agreements to Repurchase	$ 54,493	$ 84,064